The present invention relates to a non-crescent seal internal gear pump for generating high pressure, and particularly to sealing elements in the gear teeth.
A pump of this generic type is disclosed in DE 41 40 293 C2 which corresponds to U.S.Pat. No. 5,399,079.
Internal gear pumps generally have an internally toothed ring gear which surrounds an externally toothed pinion with a smaller number of teeth. The sets of teeth mesh in driving engagement at one circumferential region around the gears. As a rule, the toothing of this type of pump is relatively narrow in relation to the diameter of the pinion or of the ring gear. Because the volumetric flow to be conveyed is determined by the radial height of the teeth and the width (or axial length) of the toothing along the rotation axis, volumetric flow is limited for design reasons in current pumps. Non-crescent seal internal gear pumps have, in particular, the advantage of a minimal overall volume.
To improve the tightness of the pump between the tooth tips of the pinion and the ring gear, DE 41 40 293 C2 discloses a sealing element inserted in each of the tooth tips of the ring gear, specifically in a dovetailed profile groove in the tooth tip. The profile groove also limits the radial movement of the sealing element. The profile groove therefore virtually acts as a radial limit for the sealing element.
If the sealing element has reached its (radially outer) end position, the two side faces of the sealing element rest with an exact fit on the side faces of the profile groove. As seen over the axial direction width of the toothing, a specific defined pressure distribution is thereby no longer ensured. This may lead to undefined or variable operating states of the pump.